As you say, getTexture () after bind () did not return null.
No exception is raised at runtime.
I considered another drawing method.
So, refer to
net.minecraft.client.gui.screen.EditSignScreen
TileEntityRendererDispatcher.instance.render (TileEntity, Double, Double, Double, Float);
By using, the texture was successfully drawn.
However, when text is written on the signboard, the texture is not drawn correctly and the text texture is displayed (see image).
Is there a solution for this?